1. Technical Field
This invention relates generally to infusion systems for the administration of medications, and more particularly to a new and improved infusion system that is subcutaneously implantable.
2. Background Information
An implantable infusion system generally includes a reservoir within a housing having a size, shape, and biocompatible exterior suitable for subcutaneous positioning within a patient's body. Medications to be administered are periodically injected into the reservoir using a syringe by inserting the needle through a self-sealing dome on the housing, and a catheter is positioned to direct the medications from the reservoir to a selected portion of the patient's body. A pump and valving arrangement transfers the medications from the reservoir to the catheter under patient control, and this allows the patient to administer required medications in precise quantities while minimizing the number of injections required and the number of visits made with a physician.
However, many existing infusion systems have certain problems that need to be overcome. For example, the pump may be actuated by the patient depressing an actuator or plunger on the housing in a desired number of strokes, each stroke transferring a known dosage. As the actuator is stroked, the dosage passes through the catheter to the infusion location. Thus, the total dosage is administered substantially all at once.
Although this suffices in many cases, it is sometimes preferred that the dosage be administered more slowly at a substantially constant flow rate, a little at a time over a relatively prolonged period. In order to do this with existing infusion systems, the dosage per stroke must be kept small and the actuator must be stroked again and again during the entire period of administration. Thus, the patient must expend more time and effort than preferred while remaining relatively attentive to the administration procedure. Even under these conditions, a continuous flow cannot be secured because of the instantaneous discharge of the small doses. Consequently, it is desirable to have a new and improved infusion system that overcomes these concerns--one capable of administering the dosage more slowly with less patient involvement at a more continuous flow rate.
Another problem with various existing infusion systems is their inability to store multiple dose quantities at one time. Also, many are electrical in operation, requiring batteries or the like, and running the risk of a sudden, unexpected loss of power.
Finally, the existing systems that do solve some of these problems require surgical implantation of more than one part, each part usually in a separate incision resulting in extensive tissue damage. The parts are connected together during surgery, thereby increasing the difficulty of the implantation procedure and the cost and risk to the patient.